Abstract: The traditional flow laws are inapplicable to the tight sand gas reservoirs because of the reservoirs’ rather low
porosity，low permeability and the high effective stresses. On account of the tight gas flow features and flow fields around the
horizontal wells，the horizontal well flow zone is divided into two areas：the near-wellbore area，which is non-Darcy flow，
and the far-away area from the wellbore，which is Darcy Flow. Based on the study of this division，start-up pressure gradient，
slippage effect and stress sensitivity，the productivity equation of horizontal wells in tight sand gas reservoirs was derived. A
case study is presented with the detailed studies on the three factors which impact the tight gas reservoir. With the equation
and the case study analysis，the results indicate that：（1）productivity of horizontal wells in tight sand gas reservoirs decreases
with start-up pressure gradient and stress sensitivity at a linear and an exponential relationship，respectively，but increases with
slippage effect at a near-linear relationship；（2）the stress sensitivity has a stronger impact on the productivity compared with
the start-up pressure gradient，and the influence of slippage effect is relatively small.

Key words: tight sand gas reservior, Darcy flow area, non-Darcy flow area, start-up pressure gradient, slippage effect, stresssensitivity